Optical transmitter and quantum communication system

Abstract

A quantum transmitter 501 for use in a quantum communication system is provided, the transmitter comprising: a plurality of quantum state encoders 108, each encoder configured to emit portions of light, each portion encoded with a respective quantum state; and a beam combining module 402 configured to receive portions of light emitted from each quantum state encoder, and combine the received portions to produce output light comprising a sequence of successive portions of light emitted by each encoder. A corresponding quantum communication system is also provided. The output from the beam combiner may be time-division multiplexed pulses from respective encoders. The time division may be effected using different delays in the lines between encoder and combiner or may be effected with offset drive signals to the encoders or with selective switching at the combiner. Using multiple encoders allows an increased pulse rate and also provides redundancy in case an encoder fails. The encoders may output light with a common wavelength. [Figure 5]